Seed sensor with lightpipe photodetect assembly

ABSTRACT

In one example embodiment, a seed sensor is disclosed adapted to fit a conventional mounting location in existing seed tubes that provides improved performance by providing a wide light source (more LEDS), a wide photodetector and a current profiling scheme for the LEDs that provides more light at the opposite ends of the LED array. A result of such an arrangement is to improve seed resolution and to reduce seed spatial variability within the seed tube.

CLAIM OF PRIORITY

This application is a continuation of application having Ser. No.14/424,131 and a filing date of May 6, 2015, now U.S. Pat. No.9,913,425, which claims priority to and the benefit of PCT applicationPCT/US2013/056772, filed on Mar. 6, 2014, which in turn claims thepriority to and the benefit of provisional patent applications No.61/698,163 filed on Sep. 7, 2012 and No. 61/693,573 filed on Aug. 27,2012, respectively, all applications of which are hereby incorporated byreference in their entireties.

BACKGROUND

As is known in the art, a field seed planter includes a group of seedchutes or seed discharge tubes, one for each row for simultaneousplanting. Each of these seed chutes or tubes convey individual seedsfrom a seed dispenser in conjunction with a hopper or other seed supplyto individual furrows formed in the ground by the planter as it movesacross a field. Various monitoring and counting arrangements have beenutilized for obtaining a count of the number of seeds dispensed by suchseed planters. Such counting is particularly useful in determining andcontrolling the density or population of seeds planted in order tooptimize crop yield. Also, more recently, seed spacing information is ofinterest since yield is positively affected by the uniform spacing ofsuch seeds.

The prior art has generally utilized photoelectric devices to sense thepassage of individual seeds through the seed chutes or tubes. Sucharrangements generally have included a light source such as a lightemitting diode (LED) positioned to one side of the seed chute or tubeand a light responsive element such as a photoresponsive transistor ordiode positioned at the opposite side of the tube. Hence, thephotoresponsive element normally produces a steady state signal level inresponse to the light incident thereupon from the light source. However,as a seed passes through the chute and comes between the light sourceand light responsive element, the level of light incident upon the lightresponsive element momentarily decreases. Responsively, the lightresponsive element produces a momentary change in the normal or steadystate signal level output, which represents potentially a seed.

Various electrical and electronic circuits have been devised to receivethe light responsive element output signal and respond to the changes inthe level thereof due to the passage of a seed through the seed chute.Ideally, such electronic circuits should produce a discrete signal orpulse for each seed passing through the chute. Accordingly, accurateinformation as to the number of seeds dispensed by a given chute may beobtained by counting these pulses.

However, various challenges to accuracy of seed counting are encounteredincluding considerable dirt, dust and the like as the planter movesthrough the field. Moreover, various coatings are commonly provided onseed grains, and these coatings often accumulate in the seed chutes ortubes. Accordingly, the foregoing accumulations of material in the seedtube tend to interfere with proper operation of the photoresponsivesystem. Additionally, the characteristics of the photoresponsive elementand light source change somewhat over time, thus changing both theambient light level incident upon the photoresponsive element and itsresponse thereto and to changes in light level due to the passage ofseeds. These changes may, if uncompensated for, greatly reduce thereliability of the response of the photoresponsive element. A relatedproblem is that of drift or changes over time in the nominalcharacteristics of the circuit elements utilized in the electroniccircuits. For example, various circuit parameters such as gain, voltagelevels, or the like may vary or drift somewhat over time. Such drift mayoccur for example due to environmental changes, detracting from optimumoperation of the circuits and hence from the reliability of the countobtained therefrom.

Yet another challenge occurs as seed deposition rates increase theability to reliably count multiple seeds which fall through the seedchute in close proximity or even partially overlapping decrease. In suchinstances, both the photoresponsive element and the associatedelectronic circuit may be unable to respond rapidly enough to reliablyproduce a separate counting pulse for each seed. A related problem isoften encountered with relatively small, fast moving seeds such assoybeans. Additionally, soybeans are generally dispensed at a relativelyhigh rate or density. Hence, today's seed sensing systems may beincapable of sufficiently rapid response to reliably count each seed andto distinguish between seeds and dust or other foreign matter.

SUMMARY OF INVENTION

In one example embodiment, a seed sensor was developed to fit theconventional mounting location on existing seed tubes but still provideimproved performance over the current production sensors by providing awide light source (more LEDS), a wide photodetector and a currentprofiling scheme for the LEDs that provides more light at the oppositeends of the LED array. A result of such an arrangement is to improveseed resolution and to reduce seed spatial variability within the seedtube.

In one example embodiment, a seed counting device is provided forcounting seeds passing through a longitudinal portion of a seed tubehaving a front, back and two side walls, the counting device including asensor assembly adapted to be mounted on a front and back wall of theseed tube, said sensor assembly including an LED (light emitting diode)array disposed opposite a photodetector device adapted to receive lightfrom the LED array, the photodetector device configured to generatesignal pulses in response to interruptions in light received from theLED array, the LED array comprised of a plurality of LEDs that aredisposed in a line that is substantially perpendicular to thelongitudinal portion of the seed tube. The seed counting device furtherincludes a controller means configured to control a current driving eachof the plurality of LEDs so as to generate a current profile for aselected LED array, controller means further configured to increase thedrive current of at least one LED located adjacent to the tube side wallso as to increase its intensity, thereby improving spatial positiondetection of seed counting device of a seed passing through the seedtube and allow for adjustments to improve seed deposition accuracy.

In another example embodiment, a particle detection system is providedwith improved spatial position detection for substantiallydistinguishing among particles such as seeds and dust, the particlecounting system including a sensor assembly adapted to be mounted onopposite sides of a chute member through which the particles are to passthrough, the sensor assembly including an LED (light emitting diode)array disposed on the chute member opposite a photodetector deviceadapted to receive light from the LED array, the photodetector deviceconfigured to generate signal pulses in response to interruptions inlight received from the LED array, the LED array comprised of aplurality of LEDs that are disposed in a line that is substantiallyperpendicular to the longitudinal axis of the chute member. The particledetection system also including a controller means configured to controla current driving each of the plurality of LEDs so as to generate acurrent profile for a selected LED array, controller means furtherconfigured to increase the drive current of at least two LEDs located ateach end of the LED array so as to increase its intensity, therebyimproving spatial position detection of the particle passing through thechute member and allow for adjustments to improve particle depositionaccuracy. In a related embodiment, wherein controller means isconfigured to individually pulse the LEDs in the array so as to improveparticle detection and deposition. In another related embodiment,controller means is configured to communicate with a particle depositionsystem so as to modify a ground speed of the deposition system as afunction of a particle detection data received by controller means.

In yet another example embodiment, a method for detecting seeds in aseed deposition system is provided having an LED array and aphotodetector member adapted to receive light from the LED array, thephotodetector member generating a signal pulse as a seed interrupts thelight received by the photodetector member. The method includes thesteps of selecting an LED array with a predetermined number of LEDs as afunction of the type of seeds to be detected and the step of generatinga current profile for a selected LED array depending on the number ofindividual LEDs in the array and the type of seeds to be detected. Themethod also includes the step of driving the current in at least twoLEDs at each end of the LED array such an intensity of the at least twoLEDs is higher than the LEDs disposed therebetween.

In yet another example embodiment, a seed counting device is providedherein with improved spatial position detection of a seed passingthrough a seed tube so as to allow for adjustments that will improveseed deposition accuracy and crop yield in seed farming applications. Aseed counting system is also provided herein with improved spatialposition detection for substantially distinguishing among seeds,multiple seeds, and foreign material such as dust in seed farmingapplications.

DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 14 are a top, cutaway view and a perspective view of a seedtube with a seed dropping through the tube with an LED array on one endand a photodetector on the other (there is also a clear window in frontof the photodetector). Both the LED source and the photodetector coverthe entire width of the tube.

FIGS. 2A-2B illustrate circuit diagrams of a 10 LED array and a widephotodetector of FIG. 1 where the output is used for data acquisitionduring the testing process.

FIGS. 3A-3C illustrate front, side and rear views of the LED sourcearray of a sensor assembly according to the invention.

FIG. 4 illustrates an alignment exercise for an LED of the invention andthe photodetector in a seed tube in the vertical direction.

FIG. 5 illustrates a variability graph of a 10 LED sensor assemblyreflective of the data provided in Table 1 of the specification.

FIG. 6 illustrates a variability graph of a 3 LED sensor assemblyreflective of the data provided in Table 2 of the specification.

FIG. 7 illustrates a circuit diagram of an embodiment of a sensorassembly according to the teachings of the invention.

FIGS. 8A-8C illustrates top, back and side views of a lightpipe or lenselement for use in connection with a seed sensor assembly according tothe teachings of the invention.

FIGS. 9A-9B illustrate side and top views of a lightpipe or lens elementwithin a seed tube for capturing light projecting therethrough for usein connection with a seed sensor assembly according to the teachings ofthe invention (top view, multiple arrows; side view, one arrow).

FIGS. 10A-10D illustrate side and top views of a lightpipe with orwithout a circuit board (view A) and at least two lightpipes with orwithout a circuit board (view B) for using in connection with a seedsensor assembly according to the teachings of the invention.

FIG. 11 illustrates an LED projecting two beams of light through a lenselement through to two detectors for potential dust detection accordingto the teachings of the invention.

FIG. 12 illustrates a lightpipe assembly or lens at one end and amicrophotodetector at another end as an embodiment of an element in aseed sensor assembly according to the teachings of the invention.

FIG. 13 illustrates a lightpipe assembly with a Fresnel lens at one endand a microphotodetector at another end as an embodiment of an elementin a seed sensor assembly according to the teachings of the invention.

FIG. 14 illustrates a seed tube with a circuit board having a 10 LEDarray that is disposed behind a clear plastic window and the assembly ofwhich is secured to one side of the seed tube.

DESCRIPTION OF THE INVENTION

Following are more detailed descriptions of various related conceptsrelated to, and embodiments of, methods and apparatus according to thepresent disclosure. It should be appreciated that various aspects of thesubject matter introduced above and discussed in greater detail belowmay be implemented in any of numerous ways, as the subject matter is notlimited to any particular manner of implementation. Examples of specificimplementations and applications are provided primarily for illustrativepurposes.

Referring now to FIG. 1, there is shown one example embodiment of a seedsensor assembly 100 in a seed tube 102. Specifically, there is shown atop, cutaway view of seed tube 102 with a seed 104 dropping through thetube with a 10 LED array 110A-110J on one end and a photodetector member120 on the other (in this example embodiment there is also a clearwindow in front of the photodetector). This figure shows a top view ofseed tube 102 with one seed 104 free-falling. Both the 10 LED array andthe photodetector member are spaced back from the tube's (or chute's)inner wall slightly and photodetector 120 extends slightly beyond thechute's inner wall in an orthogonal direction (orthogonal to thedirection of the falling seed and the length of the seed tube). In thisexample embodiment, the photodetector is the 880×110 unit (dimensions inmils) covering the full width of seed tube 102 (700 mils). The 10 LEDarray also attempt to span the entire width of tube 102 providing lightrays over the entire area including near the side walls 103A-103B. Thisexample embodiment of sensor assembly 100 consists of a 10-LED array on72 mils pitch. FIG. 14 is an example of a circuit board with the 10-LEDarray that is disposed behind a clear plastic window plate that issecured on one side of the seed tube, opposite a photodetector. Inrelated embodiments, the LED array does not use a window plate or iscoated with a special coating to protect the array surface and/or slowsdown the surface degradation of the array. In related embodiments, theLED array comprises other combinations such as one 3-LED array or a5-LED array, each of which can be optimized to improve seed counting andidentification by varying the current profiling scheme of the LED arrayused.

Although this example sensor assembly provides various improvements overcurrent sensors (in the example embodiment, at least three), one or moreof these improvements are combined and incorporated into variousembodiments of sensor assemblies. A first sensor assembly improvementincludes a wide light source comprised of 10-LED array 110 (LEDs110A-110J) of LEDs that are spaced evenly across the narrow dimension ofseed tube 102. The ten (10) SMD (surface mount devices) LEDs stillprovide a pitch dimension that would allow the LEDs to be“Pick-n-Placed” by conventional component placement equipment. The tenLED array in this example configuration also provides a fairly evenlight source considering the dimensions of the seeds falling through thetube. The individual LEDs at each end of array 110 were very close toside walls 103A and 103B of tube 102, thereby providing light coverageacross the whole tube. Another improvement illustrated in FIG. 1includes the use of a wide photodetector member 120 that is 880 milswide to cover the entire width of the seed tube versus currentphotodetectors which are 600 mils wide while the inner seed tubedimension is about 700 mils wide.

Referring now to FIGS. 2A-2B, in this example embodiment there are showncircuit diagrams 210 and 220 of 10-LED array 110 and of photodetector120 of FIG. 1, respectively. Circuit 210 illustrates LED array 110 withthe LED drive circuitry and circuit 220 illustrates the opposing endcircuitry for the photodetector and transmission of data (output 250) toa data acquisition system. In this example embodiment, the current isincreased for each of the LEDs at each end of the LED array (e.g., 110Aand 110J) to improve upon spatial variability according to the teachingsherein. Extra current is provided to the two extreme LEDs as well as theadjacent LEDs (e.g., 110B and 1100 in from the extreme LEDs (LEDs 110Aand 110J). Pulses received at photodetector 120 are eventually outputted(output 250) to a data acquisition system. Ordinarily, this output wouldgo to an A/D converter of an embedded controller for processing (such astaught in U.S. Pat. No. 5,635,911 to Landers et al, and is incorporatedby reference herein in its entirety). This circuit 220 provides “0”voltage bias to photodetector 120 to obtain a speed advantage and atrans-impedance amplifier 224 then converts the short-circuitphotodetector current to a voltage. In addition, this amplifier servesas a log amplifier which is used to provide a consistent voltage pulsefor a given blockage percentage no matter the ambient opticalattenuation. A level shifter 226 is also provided here to keep thesignal in a dynamic range. A fixed gain amplifier (222) is shown herefor experimental testing. Several gain options would be available underthe power of the embedded controller (see also FIG. 7 for more completedescription of the seed counting system from a circuit levelperspective).

Referring again to FIGS. 1 and 2, another improvement in the sensorassemblies described herein includes the use of Current Profiling forthe LEDs located at each end of the LED array (such as 110A, 110B, 110Iand 110J) closest to the tube walls (103A and 103B). In this exampleembodiment (and as described above), the wider LED array 110 and widerphotodetector 120 provide coverage that aid in reducing the spatialvariability between seeds. Hence a seed falling (e.g., seed 104)anywhere in the seed tube sensing area (space 105 between walls 103A and103B) will provide much the same signal shape. However, seeds fallingnear side wall 103A or 103B typically do not have the same blockage oflight (which generates the signal pulse that represents the seed count)as seeds falling closer to the center of space 105. In LED array circuit210, LED 110A corresponds to LED 110A at one end of array 110 and LED110J corresponds to LED 110J of array 110 at the other end of the arrayon the seed tube wall. To help compensate or correct for this, in oneexample embodiment, the LED current in each of the two extreme end LEDs(LEDs 110A and 110J) is increased to a factor of 1.50 times that ofnominal. The next two LEDs are increased by a factor of 1.25. This tendsto weight seeds near the side wall more heavily in that they block alarger amount of light. Other LED currents may require adjusting yet toobtain optimum variability.

A result of the various improvements described above to reduce spatialvariability, is that single seeds falling through the seed tube willgive much the same signal pulse in terms of amplitude, area, andduration. This allows an algorithm used to differentiate singles fromdoubles from triples to function better. This consistency in pulsecharacteristics allows for a cleaner separation between single seeds anddouble seeds (two seeds falling through the sensing area at much thesame time). This also applies to separation of doubles and triples, andso forth. This consistency also helps differentiate between seeds andforeign material. Dust particles can more easily be segregated fromseeds and thus not counted.

In another example embodiment, the accuracy count of the seed sensor isimproved by the use of Current Profiling along with the expanded LEDarray and larger photodetector member when seeds are falling through thesensor at a high rate and are not well singulated. This is particularlya problem with high rate soybeans. This improvement in count accuracy isdue to reduced spatial variability of single seed pulses which allowseasier separation of seeds falling at about the same time. In yetanother related embodiment, seed sensing is improved when implementingthe technique of individually pulsing the LEDs in the array. It wasdetermined that a current profile of 1.5/1.25/1.0 would be optimal andoperational for the targeted applications, but is not limited to thisrange.

Referring now to FIGS. 3A-3C, there are shown front, side and rear viewsof a sensor housing to support an LED array according to the invention.In this example embodiment and with reference to FIG. 14 as well, LEDarray 110 is disposed on circuit board 112 and covered with a clearwindow plate 119. This assembly is coupled to seed tube 102 via afastening member 109. In other related embodiments, other fasteningmeans can be used depending upon tube 102 construction or that of theLED array, the window plate may be eliminated.

Referring now to FIG. 4, there is shown an example of an alignmentexercise for an LED and the photodetector in a seed tube in the verticaldirection. Since the tube walls of interest are not parallel, it isestimated that a 3 degree correction is needed.

In this example embodiment, 10-LED array 110 was configured to providethe same optical intensity to photodetector member 120 as a 3-LED array.In order to get the 10-LED array to the same level as a 3-LED array, theLED current was set to a nominal (333/178) 6 ma=11.2 ma. Consider thefollowing:

Center Leg=12 ma

Right Leg=12+6+3=21 ma

Left Leg=12+6+3=21 ma

Total Current=48 ma (3 ma in the right & left legs are common to twoLEDs)

Tables 1 and 2, respectively, provide data from a 10-LED array and a3-LED array variability test and illustrate the voltages from the firststage trans-impedance amplifier when a 0.19 inch diameter vertical rodis used to block the light between the light source (such as the LEDarray) and the photodetector. The data is gathered from a top view ofthe seed tube and shows the position of the rod for correspondingvoltages for the 10 LED array (Table 1) and also for comparison aprevious 3 LED array (Table 2). The position of the voltage labels inthe tube correspond to the position of the rod.

TABLE 1 Increased LED current Top View 10 LED No Seed 05.61 355.83310.550 0.551 0.549 0.546 0.543 0.548 Photodetector 0.543 0.541 0.546 LEDs0.545 0.543 0.545 0.550 0.549 0.545These are top views of the tube with voltages from the 1^(st)trans-impedance amplifier when blocking light with a vertical 0.19 inchdiameter rod.

TABLE 2 3 LED No Seed 0.562 363.584 0.551 0.553 0.551 0.544 0.539 0.544Photodetector 0.536 0.535 0.536 LEDs 0.543 0.541 0.543 0.546 0.551 0.546

FIGS. 5 and 6 illustrate LED profile and light intensity variabilitygraphs for the 10 LED and 3 LED sensor assemblies, respectively, asdescribed previously. The LED profile pertains to increasing the currentof the LEDs at the far end of the array closest to the side walls tocompensate for the reduced light blockage of a seed located near theside wall. For these graphs, the photodetector short circuit current isshown in units of p.a. These were reverse calculated from the measuredvoltages from the 1^(st) trans-impedance amplifier. Note that withgreater light coverage in the tube with the 10-LED array and the use ofcurrent profiling that the variability is less, hence having a flatteror more even profile then with the 3-LED array.

Referring now to FIG. 7, in this example embodiment there is shown acircuit diagram 300 of an embodiment of a seed sensor assembly that usesan STM32F101C6T6 microcontroller 302 according to the teachings of theinvention. The front end of circuit 300 includes LED circuit 210 andphotodetector circuit 220. The output from the front end orphotodetector circuit 220 provides input to the embedded A/D(analog-to-digital) converter of controller 302. The seed countingalgorithm functions are based on the digital information from the A/D.Power supply and other support circuits are shown that enable theinvention and algorithms. The sensor assembly provides a single-endoutput that can also be used by the sensor assembly to receive data froma central control unit. An example of such communications would be arequest by the control unit for the sensor assembly to perform aself-test. The embedded controller can modulate some of the LEDs suchthat a self-test can be conducted by the sensor assembly with resultstransmitted to the control unit.

In a related embodiment, a seed sensor assembly is provided thatsubstitutes a single discrete photodiode for the wide photodetector.This detector resides on a circuit board and a light pipe or light tubeor prism channels light from the LEDs to the photodetector diode. Inanother related embodiment, a Fresnel lens 800A is used in place of thewindow plate in front of the photodetector (PD) 920 in order to capturemore light from the LEDs (see FIGS. 13 and 14).

Referring now to FIGS. 8-14, FIGS. 8A-8C and 12 illustrate various viewof a lightpipe or lens element 800 (or optical adapter) for use inconnection with a seed sensor assembly according to the teachings of theinvention. In this example embodiment, lightpipe member 800 includes afront surface 802 for receiving light that is focused to a back end 804.Instead of directly coupling light into the photodetector, in thisexample embodiment, optical adaptor element 800, which is made of glassor/and plastic, is inserted before the photodetector.

Referring now to FIGS. 9A-9B, there is shown side and top views of alightpipe or lens element 800 located within seed tube 102 having LEDarray 110 that generates light 111. Lightpipe 800 captures light 111projecting therethrough from array 110 for use in connection with a seedsensor assembly according to the teachings of the invention. Inparticular, there is shown a detector assembly 920 of a small areadetector coupled to an optical adaptor (or lightpipe). In this example,the optical adaptor transforms the detection area into a long slit whichis desirable in seed sensing/counting applications. The back end 804(exit) of the optical adaptor is connected to the optical sensor byglue, screw, snap, direct contact or other means. The front end 802(entrance or light receiving end) of the optical adaptor sits where theoptical sensor was, as an effective optical sensor. Light is firstlycollected by the front end (wide end) 802 of the optical adaptor,transported by reflection and total-internal-reflection (TIR), andeventually coupled via back end 804 into the optical sensor. Thisapparatus forms a sight waveguide or light-pipe. In an alternativeembodiment, a glass window can be attached to the front end of theadaptor, to protect the adaptor from contamination, mechanical scratchesor chemical corrosion. The other part of the seed sensing system willwork as usual.

A similar configuration is proposed for the light emitter, in this case,light from an emitter, such as an LED or Laser diode, is coupled intothe waveguide at one end and travels through the waveguide to the exitend where the light will emerge to the desired location, such as theseed tube facing the detector aperture. Previous large area opticalsensors would normally cover the width of the seed tubing, therebyincreasing the price of the overall sensor assembly. The optical adaptordescribed herein transforms a much cheaper small sensor area (back endof the adaptor) into an effectively large collection area (front end ofthe adaptor). The small sensor and adaptor combination works exactly asthe large area sensor, but costs much less and offers more flexibilityin mechanical layout since the adapter may have bends and turns in it.Adapters could be machined parts or molded so as to reduce its costfurther. Using the optical adaptor, the sensing area can be effectivelyand easily reshaped without having to reconfigure other hardwarecomponents of the seed sensor. The optical adaptors taught herein applybut is not limited to seed sensors.

Referring now to FIGS. 10A-10D, there are shown side and top views of alightpipe 800 (and 800A and 800B) with or without a circuit board 112Aand at least two lightpipes 800A, 800B with or without a circuit boardfor using in connection with a seed sensor assembly according to theteachings of the invention. In particular, the views on the left (FIGS.10A and 10B) illustrate different configurations of optical detectors800 while the views on the right (FIGS. 10C and 10D) illustrate printedcircuit board 112A design flexibility due to optical adaptors 800A and800B. The two detectors can be very close (A′) or some distance apart(B′) using the same detector board 112.

Optical adaptors provide for flexible circuit board design, such as whenmultiple sensors are used, because the size and distance of the sensorsare limited by the area of the electrical board. In conventional design,it may be too crowded to put two sensors very close. Using sensoroptical adaptors, multiple sensors can be put together to form a sensorarray with no physical limit by the individual sensor size and boardarea, and without using an array detector.

In one example embodiment, a PCB (printed circuit board) board can beshared by multiple optical sensing geometries by changing opticaladaptors to different optical setups. This lowers cost on board designs.Optical adaptors also provide for flexible array detector design, suchthat when an array detector is desired, the number of elements may notalways be available. Hence, it effectively couples light into sensorarrays of different shapes with much lower loss than a mask. All of theabove applies to the use of the adaptor as a light emitter as well asdetector.

Referring now to FIG. 11, it illustrates an LED 1110 projecting twobeams of light 1111A-1111B through a lens element within a seed tube 102through to two detectors 1120A-1120B for potential dust detectionaccording to the teachings of the invention. In particular, the twoclose beams of light provide similar attenuations for dust with eachdetector being vertical to one another. A seed 104 drops from the top tothe bottom (arrow) while dust can come from both directions, which canbe detected and rejected as dust counts. The time-of-flightdistributions can also be used to reject non-seed events.

The two detectors referred to above can be placed at the front end of anoptical detector as shown in FIG. 12, which is a lightpipe assembly orlens at one end and a microphotodetector at another end, in an exampleembodiment of an element in a seed sensor assembly according to theteachings of the invention. In particular, the light is coupled to thedetectors more efficiently, improving sensor operation withoutincreasing cost substantially.

Referring now to FIG. 13, it illustrates a lightpipe assembly 800A witha Fresnel lens 810 at one end and a microphotodetector at another end asan embodiment of an element in a seed sensor assembly according to theteachings of the invention. In this example embodiment, the Fresnel lensassists in channeling light even further into the optical adaptor.

The following patents that relate to seed sensor devices are hereinincorporated by reference in their entirety and constitute part of thedisclosure herein: U.S. Pat. Nos. 4,163,507; 4,307,390; 4,555,624;4,496,211; 5,307,430 and 5,635, 911.

Having thus described several illustrative embodiments, it is to beappreciated that various alterations, modifications, and improvementswill readily occur to those skilled in the art. Such alterations,modifications, and improvements are intended to be part of thisdisclosure, and are intended to be within the spirit and scope of thisdisclosure. While some examples presented herein involve specificcombinations of functions or structural elements, it should beunderstood that those functions and elements may be combined in otherways according to the present invention to accomplish the same ordifferent objectives. In particular, acts, elements, and featuresdiscussed in connection with one embodiment are not intended to beexcluded from similar or other roles in other embodiments. Accordingly,the foregoing description and attached drawings are by way of exampleonly, and are not intended to be limiting.

1-20. (canceled)
 21. A seed counting sensor for use with seedingmachines, the sensor comprising: a detection chamber or area within ahousing or seed tube, the detection chamber or area allowing the seedsto pass through the sensor having a center longitudinal axis extendingin the flow direction of the seeds; a plurality of light sourcesarranged within the housing or seed tube at predetermined distances fromeach other, the light sources being in a plane extending substantiallyperpendicularly to the center axis of the sensor; a plurality of lightdetectors arranged within the housing or seed tube at predetermineddistances from each other, the light detectors being in substantiallythe same plane as the light sources, wherein the number of the lightdetectors equals the number of the light sources; and a signalprocessing unit or controller for controlling operation of the lightsources and for processing electronic signals produced by the lightdetectors in response to interruptions of light received from the lightsources; wherein the sensor further comprises optical adapters arrangedin front of the light sources and the light detectors, respectively, theoptical adapters configured to form a sight waveguide to channel lightfrom the light sources to the light detectors; wherein the light sourcesare separated from each other, and wherein the light sources and thelight detectors are arranged in the plane so that they are capable ofscanning substantially the entire cross section of the detection chamberor area.
 22. The seed counting sensor according to claim 21, wherein thelight sources are LEDs and the light detectors are phototransistors. 23.The seed counting sensor according to claim 21, further comprising acontrol circuit for regulating the light intensity of the light sourcesas a function of the light intensity detected by the light detectors.24. The seed counting sensor according to claim 23, wherein thecontroller and the control circuit change a drive current of the lightsources caused by dust in the seed tube.
 25. The seed counting sensoraccording to claim 21, wherein the optical adapter are made of plastic.26. The seed counting device of claim 21 further comprising a window ora light transmissive plate protecting the light sources.
 27. A method ofimproving seed detection within a seed tube caused by deterioratingoptical properties of one or more seed sensors, the method comprisingthe steps of: providing a sensor assembly adapted to be mounted on theseed tube, the sensor assembly including a plurality of light sourcesdisposed opposite a plurality of photodetectors adapted to receive lightfrom the light sources, the photodetectors configured to generate outputcurrent signals in response to interruptions in light received from thelight sources, the light sources being disposed in a line that issubstantially perpendicular to a longitudinal axis of the seed tube;processing the output current signals received from the light detectors;and controlling a current driving each of the plurality of light sourcesand changing the drive current of the light sources to increase theintensity of light in the seed tube received by the light detectors. 28.The method of claim 27, wherein the light sources are LEDs and the lightdetectors are phototransistors.
 29. The method of claim 27, wherein thelight sources include a window protecting the light sources anddeterioration of the optical properties of the seed sensors is caused byat least one of pelleting agents deposited on the windows and dust. 30.The method of claim 27, further comprising the step of providing anoptical adapter to at least one of the light detectors to collect lightfrom the corresponding light source.
 31. The seed counting device ofclaim 21 wherein the controller is configured to substantiallydistinguish among multiple seeds.